Aerosol containers are widely used to package a variety of fluid materials, both liquid and powdered particulate products. Typically, the product and a propellant are confined within the container, at above atmospheric pressure, and the product is released from the container by manually opening a dispensing valve to cause the pressure within the container to deliver the product through the valve and connecting conduits to a discharge orifice.
The dispensing valve, crimped to a mounting cup having a sealing gasket, is normally mounted in a top opening of the container, which opening is defined by a component commonly referred to as the "bead" of the container opening. The mounting cup includes a central pedestal portion for holding the dispensing valve, a profile portion extending outward from the pedestal portion, which profile portion merges into an upwardly extending body portion, the body portion emerging into a hemispherically-shaped channel portion terminating in an outer skirt portion, which channel portion is configured to receive the bead portion of the container opening. The sealing gasket normally is disposed within the channel portion and in many gasket configurations extends downward along a part of the body portion. After the sealing gasket is disposed onto the mounting cup, the cup is positioned onto the container and the cup is clinched to the container. The clinching operation is well-known to those skilled in the aerosol container art.
Aerosol mounting cups are usually manufactured by stamping, drawing and, ultimately, cutting the mounting cup from a sheet of the metal fed to the die and cutting equipment. While the outer or skirt portion of the mounting cup is usually depicted in drawings thereof as being straight, the reality is that the cups of the prior art have a slightly outwardly flared skirt, the edge of which skirt is often burred. See FIG. 1.
The magnitude of the outward flare and burr can vary within the press tooling and is related to the tooling in the final trim and draw operation, i.e., trim and draw punch, trim and draw die, and the inner curling punch. The above problems are caused by the progressive wear and clearance between punch and die, e.g., new punches with standard clearance of 0.0015 maintain a sharper cut edge (minimum burr). However, during the course of production of large quantities, the formation of the flare and burr is a common occurrence.
The metal mounting cup is often coated with a thin protective plastic coating so as to protect the metal against the corrosive effects of the product to be stored within the aerosol container as well as the ambient conditions of the environment. In commerce, mounting cups, with or without valves, are loosely packed in boxes and shipped to another site for assembly with the other components of the valve mounting assembly and, subsequently, shipped to the party (filler) that fills the aerosol container with product and propellant and affixes, in a sealing relation, the valve mounting assembly and the filled container. In shipment, the mounting cups are free to move and to shift within their container with the consequence that the sharp outwardly flared, often burred, outer edge of the skirt portion of the mounting cup scratches the external tin coating on tinplate mounting cups, as well as the thin plastic and lacquer coatings on steel and aluminum cups.
Additionally, in the mass production of aerosol valves, the application of the gasket to the mounting cup and the assembly of the valve to the mounting cup involve moving the mounting cups in a continuous line along a track from station to station. As a consequence, adjacent mounting cups in the tracking line have essentially a point contact, i.e., flared edge to flared edge, when moving along the track, rather than the more desirable surface to surface contact of the skirt portion of each cup. Often, the point contact of the flared edges results in damage to the mounting cup.